package org.apache.maven.model.building;

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.Collections;
import java.util.List;

import org.apache.maven.model.Model;

/**
 * Signals one ore more errors during model building. The model builder tries to collect as many
 * problems as possible before eventually failing to provide callers with rich error information.
 * Use {@link #getProblems()} to query the details of the failure.
 * 
 * @author Benjamin Bentmann
 */
public class ModelBuildingException extends Exception {

  private final ModelBuildingResult result;

  /**
   * Creates a new exception with the specified problems.
   * 
   * @param model The model that could not be built, may be {@code null}.
   * @param modelId The identifier of the model that could not be built, may be {@code null}.
   * @param problems The problems that causes this exception, may be {@code null}.
   * @deprecated Use {@link #ModelBuildingException(ModelBuildingResult)} instead.
   */
  @Deprecated
  public ModelBuildingException(Model model, String modelId, List<ModelProblem> problems) {
    super(toMessage(modelId, problems));

    if (model != null) {
      DefaultModelBuildingResult tmp = new DefaultModelBuildingResult();
      if (modelId == null) {
        modelId = "";
      }
      tmp.addModelId(modelId);
      tmp.setRawModel(modelId, model);
      tmp.setProblems(problems);
      result = tmp;
    } else {
      result = null;
    }
  }

  /**
   * Creates a new exception from the specified interim result and its associated problems.
   * 
   * @param result The interim result, may be {@code null}.
   */
  public ModelBuildingException(ModelBuildingResult result) {
    super(toMessage(result));
    this.result = result;
  }

  /**
   * Gets the interim result of the model building up to the point where it failed.
   * 
   * @return The interim model building result or {@code null} if not available.
   */
  public ModelBuildingResult getResult() {
    return result;
  }

  /**
   * Gets the model that could not be built properly.
   * 
   * @return The erroneous model or {@code null} if not available.
   */
  public Model getModel() {
    if (result == null) {
      return null;
    }
    if (result.getEffectiveModel() != null) {
      return result.getEffectiveModel();
    }
    return result.getRawModel();
  }

  /**
   * Gets the identifier of the POM whose effective model could not be built. The general format of
   * the identifier is {@code <groupId>:<artifactId>:<version>} but some of these coordinates may
   * still be unknown at the point the exception is thrown so this information is merely meant to
   * assist the user.
   * 
   * @return The identifier of the POM or an empty string if not known, never {@code null}.
   */
  public String getModelId() {
    if (result == null || result.getModelIds().isEmpty()) {
      return "";
    }
    return result.getModelIds().get(0);
  }

  /**
   * Gets the problems that caused this exception.
   * 
   * @return The problems that caused this exception, never {@code null}.
   */
  public List<ModelProblem> getProblems() {
    if (result == null) {
      return Collections.emptyList();
    }
    return result.getProblems();
  }

  private static String toMessage(ModelBuildingResult result) {
    if (result != null && !result.getModelIds().isEmpty()) {
      return toMessage(result.getModelIds().get(0), result.getProblems());
    }
    return null;
  }

  private static String toMessage(String modelId, List<ModelProblem> problems) {
    StringWriter buffer = new StringWriter(1024);

    PrintWriter writer = new PrintWriter(buffer);

    writer.print(problems.size());
    writer.print((problems.size() == 1) ? " problem was " : " problems were ");
    writer.print("encountered while building the effective model");
    if (modelId != null && modelId.length() > 0) {
      writer.print(" for ");
      writer.print(modelId);
    }
    writer.println();

    for (ModelProblem problem : problems) {
      writer.print("[");
      writer.print(problem.getSeverity());
      writer.print("] ");
      writer.print(problem.getMessage());
      writer.print(" @ ");
      writer.println(ModelProblemUtils.formatLocation(problem, modelId));
    }

    return buffer.toString();
  }

}
